What type of joints should I use for this fish tank stand?

[tennents]

It'll be made of 2 x 4's with 18mm plywood all around. It needs to be able to support around 350kg in weight from the fish tank, water, and aquascaping. Not shown in the drawing is there'll be diagonal bracing on the back side.

I'm a beginner at wood working. The one decent tool I have is a bosch 800 SJ sliding mitre saw.

I'm wondering if I should get a kregs xl pocket jig and just glue + pocket screw each joint? Or should I try do a half lap joint, or maybe dowels? Any input appreciated, thanks

 

[JamesHow]

I would just screw it together tbh.
The outer uprights will support the weight.

 

[tennents]

I would just screw it together tbh.
The outer uprights will support the weight.

I want to make it with a bit of care as a learning experience. Screws straight in work but hoping to do something a bit more advanced than that. But overall strength matters the most, so if just screwing in two pairs of wood screw face on for each joint is best strength i'd do that and use titebond 3 for each joint too

If I go with just screwing straight in option, think I'd go for lag screws instead of regular wood screws.

 

[AJB Temple]

If you are planning to clad it all round with plywood, you will have an extremely strong box. It actually looks a bit over built to be frank. If plywood is cladding it I don't think you need the cross braces. If all joinery is hidden, then I would just screw and glue.

 

[tennents]

If you are planning to clad it all round with plywood, you will have an extremely strong box. It actually looks a bit over built to be frank. If plywood is cladding it I don't think you need the cross braces. If all joinery is hidden, then I would just screw and glue.

what kind of screws would you recommend? I'd counter sink them and do a pilot hole for each. Guess they'd have to be pretty long if im just going in face on

 

[AJB Temple]

Personally I use Reisser self countersinking and drive them in with an impact driver. Probably I would glue and tack the plywood on with an electric brad nailer set to drive them just under the surface ready for filling and painting. You may need to give some thought to corner aesthetics unless you are adept at doing mitres. A track saw would make short work of mitres but your box would need to be spot on accurate. The alternative is right angle cover pieces, readily available as mouldings from the DIY sheds. This would allow the box to be butt jointed. I have a domino machine so personally I would use that, but you need to get around your gear limitations. I would greatly simplify the frame structure personally.

 

[Robert]

Welcome to the forum. I'd agree with the overbuilt comment. Guessing based on you saying 2 x 4's it is about 900 x 400mm so it seems a waste to not use the inside for storage. Maybe try a new design using the ply to make a rigid box into which you can cut a square hole at the front for doors and just use timber for the top bottom and vertical corners.

 

[Woodbloke]

Some years ago I contemplated building a stand for a largish tropical marine tank. When I calculated the weight of water that the stand would have to support my ghasted was flabbered! Water is incredibly weighty stuff so 'belt n'braces' however it's done is the way forward....don't underestimate how much weight the stand will have to withstand! - Rob

 

[tennents]

Personally I use Reisser self countersinking and drive them in with an impact driver. Probably I would glue and tack the plywood on with an electric bad nailer set to drive them just under the surface ready for drilling an painting. You may need to give some thought to corner aesthetics unless you are adept at doing mitres. A track saw would make short work of mitres but your box would need to be spot on accurate. The alternative is right angle cover pieces, readily available as mouldings from the DSIY sheds. This would allow the box to be butt jointed. I have a domino machine so personally I would use that, but you need to get around your gear limitations. I would greatly simplify the frame structure personally.

I will be buying a track saw to cut the plywood.. didn't realise I could also use it to mitre the edge of the plywood to hide the edge grain. I was planning on just using wood filler and sanding to make the edges smooth for paint.

 

[tennents]

Welcome to the forum. I'd agree with the overbuilt comment. Guessing based on you saying 2 x 4's it is about 900 x 400mm so it seems a waste to not use the inside for storage. Maybe try a new design using the ply to make a rigid box into which you can cut a square hole at the front for doors and just use timber for the top bottom and vertical corners.

thanks, it's 900 x 450. It'll be exactly those dimensions so that the fish tank is flush. It's designed so that once the 18mm ply is added ontop it has those dimensions.

There's still internal space for filter, electrics and fish related stuff. Not a huge amount but you don't need a lot of space for that. It is probably overbuilt for the weight, I just copied a design I found online that seems to be quite commonly used for fish tank stands. There's a total of 16 vertical 2x4's in the design (3 for each corner, and 4 in the middle), not sure how much a single 2x4 vertical can hold in weight but 12 is indeed a lot of wood

 

[Mike G]

Adrian's covered it, I think. You could easily build this out of 2 x 2s and have it plenty strong enough (although you might use 4x1s for the horizontals). The ply means you don't need any diagonal bracing....and the type of screws you use is unimportant.

 

[tennents]

Would pocket holes also work tho if also use glue?

My concern is I've heard that it's not good to screw into the end grain... and if I just put screws in just face-on then they'll almost all be going into the end grain of wood.

 

[Mike G]

No, don't use pocket hole screws. There's never a good reason to use them. Make this very basic joint:


There's actually no need for any joinery at all. The plywood can support the tank entirely on its own without any frame. You could join it with those nasty little plastic joining blocks if you wanted. You could join it with 20mm x 20mm battens glued and screwed into the corners.

 

[tennents]

No, don't use pocket hole screws. There's never a good reason to use them. Make this very basic joint:

View attachment 36884
There's actually no need for any joinery at all. The plywood can support the tank entirely on its own without any frame. You could join it with those nasty little plastic joining blocks if you wanted. You could join it with 20mm x 20mm battens glued and screwed into the corners.

my mitre saw has a fixed depth stop, so lapped joints not really possible for me.

If people are saying just screw straight into the end face-on and some glue is enough then I guess I'll just do that. I'll counter sink them a bit. 2 1/2 inch for face to face butt joints and maybe 4 inch ones for face to edge joints. Can anyone recommend size of screw? Thinking M6 and making pilot holes too

 

[Mike G]

my mitre saw has a fixed depth stop, so lapped joints not really possible for me.

It's a simple job with a hand saw.

If people are saying just screw straight into the end face-on and some glue is enough .....

I'm not sure what you're trying to describe. Who has said this?

 

[Steve Maskery]

No, don't use pocket hole screws. There's never a good reason to use them.

Mike! Pocket screws are fantastic for all sorts of applications, although I agree with you that this is not one of them. The half-laps that you illustrate are a good solution as that is strong and will be invisible when finished.
If this is your first foray into woodwork it is a very good option. Mitres are difficult for all of us, personally I wouldn't recommend them for such a big edge.
Screwing into end-grain is nowhere near as strong as screwing into face-grain. If you do decide to do that you will need looooong screws.
I'm currently making an office storage unit, out of MFC, small footprint, as tall as I can get away with. It's all in pieces in the hallway at the mo that need to be brought up an unfriendly staircase. Then it will all be pocket-screwed together and look - very serviceable.
S

 

[slimshady]

Hi Dan.
I've never had a fish-tank, but, is the width at 450mm liable to tip forward. Would these be required to be fixed to a wall.

 

[tennents]

Hi Dan.
I've never had a fish-tank, but, is the width at 450mm liable to tip forward. Would these be required to be fixed to a wall.

i'll add a couple attachment points to wall

 

[tennents]

Mike! Pocket screws are fantastic for all sorts of applications, although I agree with you that this is not one of them. The half-laps that you illustrate are a good solution as that is strong and will be invisible when finished.
If this is your first foray into woodwork it is a very good option. Mitres are difficult for all of us, personally I wouldn't recommend them for such a big edge.
Screwing into end-grain is nowhere near as strong as screwing into face-grain. If you do decide to do that you will need looooong screws.
I'm currently making an office storage unit, out of MFC, small footprint, as tall as I can get away with. It's all in pieces in the hallway at the mo that need to be brought up an unfriendly staircase. Then it will all be pocket-screwed together and look - very serviceable.
S

like how long should one go into end grain?

 

[Mike G]

like how long should one go into end grain?

You don't.

 

[Raymedullary]

If you must screw into end grain, one way around it is to insert dowels into the face at right angles to the screw so you are at least partially screwing into the side of the dowel.

 

[Steve Maskery]

Screwing into end-grain is not good practice, especially if any of the forces are in the direction that will try to pull the two pieces apart.
However.
I made a set of dining chairs 20-odd years ago. The rear cross-rail was held in place with a couple of long screws into end-grain. They are still as sound today as they were when I made them. Probably 70mm screws through 22m cherry into cherry end-grain. I took the idea from Sam Maloof, and if it was good enough for him...
But we are getting side-tracked. In a dining chair like that there are no sideways forces., so I could get away with it. For this project, you have better options that are achieveable, even for a beginner. The half-laps that Mike has sketched are a good start. Not as easy as they look, because all the faces have to be smooth and flat and square. But if they are not perfect, and which of us made out first ever project perfectly (I didn't), it's not the end of the world, because your exterior skin will a) cover a multitude of sins, and b) add great rigidity, which you will definitely need with a glass tank full fo water.

BTW, I don't understand your comment about having a fixed depth stop, so half-laps are not an option. A fixed depth stop is exacctly what you need! But get your cheap hardpoint saw out, practice a bit and then start working up a sweat.

S

 

[AJB Temple]

Come on guys, it is fully clad in plywood. Fretting about screws into end grain is irrelevant. The 18mm plywood box will be bomb proof with a bit of simple framing in the corners. It would support a house

 

[tennents]

BTW, I don't understand your comment about having a fixed depth stop, so half-laps are not an option. A fixed depth stop is exacctly what you need! But get your cheap hardpoint saw out, practice a bit and then start working up a sweat.

I have a Bosch GCM 800 SJ. It has a non-adjustable depth stop. Well, it has a screw and a bolt on the depth stop, but I'm reasonably sure that bolt is too short for any adjustments. The next model up in price, the 80 SJL has an adjustable depth stop. I have wondered if I could just buy the spare parts for the 80SJL dept stop and plate and put them on my GCMSJ as that's very cheap but no idea if that'd work. Overall the two models look similar.

I could get a router and make a jig and do half-laps that way. But if you see my design, there's so many areas where 3 bits of wood are connected too each other, and I don't see how I can half lap those areas. Just overall looking at the design, I'm lost as to where the half-laps would go even if I could make them decently.

 

[tennents]

If you must screw into end grain

what I don't get, is if i'm not screwing into end grain, and screwing in at an angle instead, then how is that any different to just doing pocket holes.. except instead of using a jig I'd be doing the angle by eye which I feel with my skill, I'd bodge it

 

[Mike G]

I'm really struggling to understand this Dan. You've been given multiple alternatives to your original impractical and unnecessary design, and you don't respond to those at all. All you keep doing is asking about screws. Why?

 

[tennents]

I'm really struggling to understand this Dan. You've been given multiple alternatives to your original impractical and unnecessary design, and you don't respond to those at all. All you keep doing is asking about screws. Why?

The thread title is 'which type of joint should I use', so I'm talking about joints.

I appreciate that people consider the design to be using an unnecessary amount of wood but overbuilding something for peace-of-mind is how I want to do it. I probably have a beginner trait of not trusting in the strength of wood, because I don't get how strong it is. The design is a commonly used one for DIY fish tank stands. With up to half a tonne of glass/water/rock 95cm heigh up and with two cats runnin around, I'd rather have it over-engineered than just 'good enough' but saving a few quid on materials. Especially since I'm putting it together and not a pro.

Even if the design were altered, I'd still be trying to figure out how to join the pieces together best. Some say don't use pocket holes, some say don't screw into end grain, some say to use lap joints instead. I also don't get the difference between pocket holes and screwing in at an angle.

 

[AndyP]

Welcome to the Woodhaven Dan.
As you are discovering there will always be more than one way to skin a cat.
My own take on this is as you are new to this woodworking malarky why not take the time to learn a few basic skills? Accurate marking and cutting to the line? The half lap joints that Mike shows #13 give you the opportunity to do both safe in the knowledge that if they are not perfect your plywood facing will cover them up.
Skills learned doing something like this will serve you well in the future.

 

[Raymedullary]

I can understand your frustration and don't feel put off by negative comments. Here's the thing, the frame doesn't even need to be jointed on the corners if you just think of it as a plywood box with internal corner pieces made from 2x2 or 2x3 pine. That way the joints become a bit irrelevant and you don't even need any joint as such.
You could cut five pieces of ply then glue screw the timber corner pieces onto two sides of the box and just put the other two sides up to them and screw them together forming a big box.

 

[tennents]

Welcome to the Woodhaven Dan.
As you are discovering there will always be more than one way to skin a cat.
My own take on this is as you are new to this woodworking malarky why not take the time to learn a few basic skills? Accurate marking and cutting to the line? The half lap joints that Mike shows #13 give you the opportunity to do both safe in the knowledge that if they are not perfect your plywood facing will cover them up.
Skills learned doing something like this will serve you well in the future.

thanks. I'm looking into if my mitre saw can be made to do half laps. I've done cutting with the mitre saw for a few things before so I know it makes really nice square cuts, also put a CMT fine-cut blade on it, that thing can cut paper thin. A hand saw can be used for laps, but I'd just either find a way to do it with the mitre saw or get a router and make a jig (saw youtube videos on that).

 

[Mike G]

The thread title is 'which type of joint should I use', so I'm talking about joints.........

But you're not (unless you call a butt join a joint). Any attempt at suggesting a joint has been met with "I don't have the skills or tools".

As for over-building......as soon as you start talking about 18mm ply, you're over-building. And, as you've been told a number of times, if you want a ply box, so long as you can successfully join the edges it is ALREADY strong enough, times over, for the trivial task you're asking of it, without any frame. You're fixated on a frame you don't need.

 

[tennents]

But you're not (unless you call a butt join a joint).

yes I call a butt joint a joint, it's in the name

Butt joint - Wikipedia

en.wikipedia.org

Any attempt at suggesting a joint has been met with "I don't have the skills or tools".

A bit of a misleading generalization, I've not said I don't have the skills or tools for any particular joint, excepting lap joints.. and for lap joints I said I could buy a router or see if I can't figure out a way to make my mitre saw do them. I also said I don't want to free-hand put screws in at an angle as I think that'd end up quite bodge, and that seems to just be same as pocket hole's anyway which I can use a jig for.

 

[Mike G]

Well best of luck. I'll leave you to it.......

 

[SimonB]

Hi Dan, very much an amateur myself, and would likely be like you and want to over-engineer a design, particularly if water is involved. I wouldn't want to discourage you, but I would also take onboard with some confidence a number of the suggestions that have been made.

Looking at the design, if I were building it, I can't see anywhere where screwing into end grain is necessary with judicious positioning of the screws. Perhaps the noggins, but they appear only structural rather then weight bearing.

If you are going to use 2x4s then I don't see where a lap joint is required. If you're using larger timber for the uprights then a lap joint would make sense. As for the mitre saw, Google AI says

"The Bosch GCM800SJ does not have an integrated adjustable depth stop for trench cuts, unlike more expensive models. However, it's possible to create a makeshift depth stop by replacing the existing bolt with a longer one or by simply unscrewing and then tightening the existing bolt to limit the saw's downward travel for trenching."

 

[Robert]

I used to keep fish many years ago. My 4ft x 1ft tank was on a stand. I bought an angle iron stand made for the tank and clad it with wood to make a cupboard out of it. Just a thought...

 

[tennents]

by simply unscrewing and then tightening the existing bolt to limit the saw's downward travel for trenching."

thanks, I'll try tinkering with that. Would be nice to learn make the laps but starting to think not much point for this particular project. If you look at the top corners for example, where three pieces of wood join together on the corner, I don't think you can have a lapped 3 piece of wood joint if that makes sense.

I can't see anywhere where screwing into end grain is necessary with judicious positioning of the screws. Perhaps the noggins, but they appear only structural rather then weight bearing.
existing bolt with a longer one or by simply unscrewing and then tightening the existing bolt to limit the saw's downward travel for trenching."

thinking to just use pocket holes wherever there's an end grain joint (which is only the noggins and outermost uprights), and I guess just regular face-on for other joints that are face to face or face to edge, and a generous amount of titebond III

 

[Windows]

You might find this thread useful:

https://community.screwfix.com/threads/trench-cutting-with-a-bosch-gcm800sj-mitre-saw.276205/

 

[tennents]

bought an angle iron stand made for the tank and clad it with wood to make a cupboard out of it. Just a thought...

and people say my design is over-engineered lol

 

[tennents]

You might find this thread useful:

https://community.screwfix.com/threads/trench-cutting-with-a-bosch-gcm800sj-mitre-saw.276205/

thanks, I tried loosening the nut on the depth stop I have and made the screw poke out as much as possible, and that gets the blade about 2cm above the deck of the mitre saw, not quite enough.

I think if I can find a longer headless bolt then I could make it work. But it would be difficult to do fine adjustment to get it just right, but not impossible.

I kind of wish I'd spent a bit more for the 80SJ, for the trench cutting and it has a bigger mitre fence, I want to make a zero-clearance fence for mine and it's doable but there's just a few small holes for screws on the fence vs the 80sj fence

 

[AJB Temple]

Don't get oversensitive Dan. Mike is an architect and has pretty much built his own house. Like me he as also done a lot of timber framing and many of us here are quite familiar with complex joints, including Japanese joints. You can certainly join three pieces of wood using lap joints or you could learn to make mortice and tenon joints which are strong and have been used for centuries. Both are very basic and as Andy has suggested you can use this job as a skill builder as it will all be hidden.

I think you may be getting fixated on the machinery. In softwood that you are using (actually any wood) you can cut a lap joint in about a minute with a tenon saw. All you need is a set square, a measure of some kind (eg steel rule) and a pencil. If you want you can also use a marking knife which will help you start the saw off. Cutting straight with hand saws is a fundamental basic skill.

It is frankly a fact that if you are cladding in ply, (18mm is really heavy duty ply - you could drop that to 9mm with no problem) all you need really is a table structure with a leg at each corner and a bit of lightish bracing. The strength from the cladding will be more than ample to hold up a car, let alone your fish tank.

If you want to have bottom rails, you could use wooden dowels (broom handle maybe) so then all you need is a hole drilled in the legs. or you can buy threaded steel rod from DIY stores and use that instead of dowels. Very simple and you could make the entire thing in half a day.

With your inexperience you will find it difficult to do angle mitre cuts in ply that are not gappy, but it's worth having a go as if it doesn't work you always have my earlier suggestion of using a corner moulding to cover it. You will need a good tracksaw blade and ply, especially cheap ply, can chip badly. If you don't have the track saw yet, invest in one with a scoring function. Or get a DIY shed to cut your boards to exact size. and invest in a good tenon saw and a decent hand saw plus a few good cheap chisels (eg Narex) instead.

I have a Mafell track saw, but then I have made shed loads of BB ply drawers and cupboards. If I didn't, in your shoes, have another sheet goods project in mind, I would not spend money on a track saw.